1. Field of the Invention
The present invention relates to a road traffic information output apparatus that outputs road traffic information.
2. Description of the Related Art
Car navigation systems in the known art achieve functions of displaying a road map around the current vehicle position, calculating a recommended route from a start point to a destination, providing route guidance based upon the calculated recommended route and the like. In addition, a road traffic information communication system (VICS) provides road traffic information through FM multiplex broadcast, light beacons and radio wave beacons. The VICS is maintained and managed by the Vehicular Traffic Information Communication System Center (VICS Center). The road traffic information provided by VICS (hereafter referred to as VICS information) includes traffic jam information, traffic control information, parking lot information, service area information and parking area information.
A car navigation apparatus receives VICS information and provides the driver with road traffic information in the form of VICS information. For instance, it may display a road map in the vicinity of the current vehicle position and provide visual traffic jam information by indicating a jammed road in red, a crowded road in yellow and a road which is neither jammed nor crowded in green.
However, when the driver wishes to view traffic jam information corresponding to a position distant from the current vehicle position such as the vicinity of the destination with a car navigation apparatus in the prior art, he must scroll the display from the current vehicle position to the destination. The process of reaching the destination through such a scroll operation is very troublesome. In addition, since smooth scrolling is prohibited while the vehicle is moving, the operation becomes even more difficult. There is another problem in that since the VICS information obtained from FM multiplex broadcast only provides information on traffic information within the prefecture in which the vehicle is currently located, VICS information for the destination which is in another prefecture cannot be obtained or displayed even through a scroll operation.
In addition, there is a problem with FM multiplex broadcast in that continuity in road traffic information display ranging over areas covered by a plurality of FM stations cannot be achieved.